Chemical elements
  Molybdenum
    Isotopes
    Energy
    Production
    Application
    Physical Properties
    Chemical Properties
    Alloys
    Compounds
      Molybdenum Hexafluoride
      Fluoroxypermolybdates
      Molybdenum Dichloride
      Molybdenum Trichloride
      Molybdenum Tetrachloride
      Molybdenum Pentachloride
      Molybdenum Oxychlorides
      Chlormolybdic Acids
      Molybdenum Dibromide
      Molybdenum Tribromide
      Molybdenum Tetrabromide
      Molybdenum Oxybromide
      Molybdenum Di-iodide
      Molybdenum Oxyiodide
      Iodomolybdic Acid
      Molybdenum Sesquioxide
      Molybdenum Dioxide
      Molybdenum Oxide Blue
      Molybdenum Trioxide
      Molybdates
      Aluminium Molybdates
      Ammonium Molybdate
      Ammonium Dimolybdate
      Ammonium Paramolybdate
      Ammonium Trimolybdate
      Ammonium Tetramolybdate
      Ammonium Octamolybdate
      Barium Molybdates
      Barium Paramolybdate
      Barium Trimolybdate
      Barium Tetramolybdate
      Barium Octamolybdate
      Barium Nonamolybdate
      Beryllium Molybdate
      Bismuth Molybdates
      Cadmium Molybdates
      Caesium Molybdates
      Calcium Molybdate
      Calcium Trimolybdate
      Calcium Tetramolybdate
      Calcium Octamolybdate
      Chromium Molybdates
      Cobalt Molybdates
      Cobalt Dimolybdate
      Cobalt Trimolybdate
      Copper Molybdates
      Ferrous Molybdate
      Ferric Molybdate
      Indium Molybdate
      Lead Molybdates
      Lithium Molybdate
      Lithium Dimolybdate
      Lithium Paramolybdate
      Lithium Trimolybdate
      Lithium Tetramolybdate
      Magnesium Molybdates
      Magnesium Paramolybdate
      Magnesium Trimolybdate
      Manganese Molybdate
      Mercurous Molybdates
      Nickel Molybdates
      Potassium Molybdate
      Potassium Dimolybdate
      Potassium Paramolybdate
      Potassium Trimolybdate
      Potassium Tetramolybdate
      Potassium Octamolybdate
      Potassium Decamolybdate
      Rhodium Molybdates
      Rubidium Molybdate
      Rubidium Dimolybdate
      Rubidium Paramolybdate
      Rubidium Trimolybdate
      Rubidium Tetramolybdates
      Silver Molybdates
      Normal Silver Molybdate
      Sodium Molybdate
      Sodium Dimolybdate
      Sodium Paramolybdate
      Sodium Trimolybdate
      Sodium Tetramolybdate
      Sodium Iodomolybdate
      Strontium Molybdate
      Thallous Molybdate
      Thallous Paramolybdate
      Thallous Tetramolybdate
      Thorium Molybdate
      Uranium Molybdates
      Uranyl Octamolybdate
      Zinc Molybdates
      Zinc Trimolybdate
      Zinc Tetramolybdate
      Zinc Octamolybdate
      Zirconium Molybdate
      Permolybdic Acid
      Molybdenum Sesquisulphide
      Molybdenum Disulphide
      Dimolybdenum Pentasulphide
      Molybdenum Trisulphide
      Molybdenum Tetrasulphide
      Thiomolybdates
      Ammonium Thiomolybdates
      Ammonium Molybdosulphites
      Potassium Thiomolybdate
      Potassium Thiodimolybdate
      Potassium Dithiodioxymolybdate
      Potassium Molybdosulphite
      Sodium Thiomolybdates
      Sodium Molybdosulphites
      Molybdenum Sulphates
      Molybdenum Selenide
      Complex Molybdoselenites
      Chromates of Molybdenum
      Molybdenum Phosphide
      Molybdic Metaphosphate
      Heteropoly-compounds with Phosphorus
      12-Molybdophosphoric Acid
      9-Molybdophosphoric Acid
      172-Molybdophosphoric Acid
      Molybdohypophosphates
      Molybdophosphites
      Molybdohypophosphites
      12-Molybdo-arsenates
      9-Molybdo-arsenates
      3-Molybdo-arsenates
      Molybdenum Carbides
      Molybdenum Carbonyl
      Reddish-violet Salts
      Yellow Salts
      Thiocyanates of Molybdenum
      Molybdenum Monosilicide
      Molybdenum Sesquisilicide
      Molybdenum Disilicide
      Molybdosilicic Acid and Molybdosilicates
      12-Molybdosilicic Acid
    PDB 1aa6-1qh8
    PDB 1r27-2jir
    PDB 2min-3unc
    PDB 3uni-4f6t

12-Molybdophosphoric Acid, H7[P(Mo2O7)6]






12-Molybdophosphoric Acid, H7[P(Mo2O7)6].xH2O, which is identical with the phosphomolybdic acid described above, may be obtained by heating the ammonium salt with aqua regia and recrystallising from water containing a little nitric acid; by dissolving the yellow hydrate, MoO3.2H2O, in a hot solution of phosphoric acid and allowing to crystallise; or by adding an excess of hydrochloric acid to a solution of an alkali molybdate and phosphoric acid and then extracting the molybdophosphoric acid with ether.

It is readily soluble in water, and on evaporation the solution deposits deep yellow octahedral crystals of the 28-hydrate H7[P(Mo2O7)6].28H2O. On heating this hydrate it begins to melt at about 78° C., and a clear liquid is obtained at 98° C., from which the 12-hydrate H7[P(Mo2O7)6].12H2O may be separated in the form of minute crystals by carefully cooling to about 90° C. If the acid is crystallised from concentrated nitric acid solution, small rhombic crystals of a 22-hydrate, H7[P(Mo2O7)6].22H2O, are obtained. Many other hydrates are described by earlier investigators, but there is little doubt that such were either identical with those described above or were not pure compounds.

Salts of this acid have been prepared by treating a solution of an alkali molybdate with a small quantity of phosphoric acid; by adding a mineral acid, preferably concentrated nitric acid, to a solution containing a phosphate and a large excess of molybdate; or by boiling an aqueous solution of an alkali phosphate saturated with molybdic anhydride. The ammonium and potassium salts separate out as deep yellow micro-crystals, but the sodium salt is soluble, and is obtained by concentrating the solution when it forms yellow efflorescent rhombohedra. These salts have the approximate composition 3R2O.P2O5.24MoO3.xH2O, where R = NH4, K, or Na. Corresponding salts of barium, cobalt, nickel, manganese, and iron have also been prepared by boiling aqueous suspensions of the metallic phosphates with molybdic anhydride.

More exact information as to the nature of these compounds was obtained by a study of the guanidinium salts. The tribasic salt, corresponding with those described above, is obtained by dissolving 12 molecules of molybdic anhydride in a boiling solution of guanidinium carbonate (containing 12 molecules), adding 1 molecule of phosphoric acid, and acidifying strongly with hydrochloric acid. The salt has the composition (CH5N3)3H7[P(Mo2O7)6].10H2O, and measurements of its electrical conductivity show it to be an acid salt. If a 10 per cent, solution of guanidinium carbonate is gradually mixed with a solution of 12-molybdophosphoric acid until the deep yellow precipitate first formed redissolves in the warm solution, greenish-yellow crystals of the heptabasic salt, (CH5N3)7H7[P(Mo2O7)6].8H2O, separate on cooling. Conductivity measurements prove this to be a normal salt.

The sodium salt described above has been shown to be an acid salt of composition Na3H4[P(Mo2O7)3].19H2O. The heptabasic silver and mercurous salts formed by precipitation from solutions of 12-molybdophosphoric acid by means of the metal nitrates are very probably the normal salts of the acid.

The existence of 11- and 10-molybdophosphoric acids and their salts, although many such have been described, is not established.


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